diff --git a/src/assets/js/working_plan.js b/src/assets/js/working_plan.js
index 866681d5..4afb4a55 100644
--- a/src/assets/js/working_plan.js
+++ b/src/assets/js/working_plan.js
@@ -323,7 +323,7 @@
             } else {
                 workingPlan[id] = null;
             }
-        });
+        }.bind(this));
 
         return workingPlan;
     };